Risk Assessment of UK Skylark Populations Using Life-History and Individual-Based Landscape Models

Abstract

Following a workshop exercise, two models, an individual-based landscape model (IBLM) and a non-spatial life-history model were used to assess the impact of a fictitious insecticide on populations of skylarks in the UK. The chosen population endpoints were abundance, population growth rate, and the chances of population persistence. Both models used the same life-history descriptors and toxicity profiles as the basis for their parameter inputs. The models differed in that exposure was a pre-determined parameter in the life-history model, but an emergent property of the IBLM, and the IBLM required a landscape structure as an input. The model outputs were qualitatively similar between the two models. Under conditions dominated by winter wheat, both models predicted a population decline that was worsened by the use of the insecticide. Under broader habitat conditions, population declines were only predicted for the scenarios where the insecticide was added. Inputs to the models are very different, with the IBLM requiring a large volume of data in order to achieve the flexibility of being able to integrate a range of environmental and behavioural factors. The life-history model has very few explicit data inputs, but some of these relied on extensive prior modelling needing additional data as described in Roelofs et al. (2005, this volume). Both models have strengths and weaknesses; hence the ideal approach is that of combining the use of both simple and comprehensive modeling tools.

The Potential for the Use of Agent-Based Models in Ecotoxicology

“…Not spraying would also alter the crops grown. When these effects were taken into account the mean 4% impact of pesticides predicted in an earlier study [30] was reduced to a barely significant 1% impact [31]. However, in both studies other structural changes in the landscape management were capable of altering skylark populations by 20-50%.…”

“…Those used as examples here are Alauda arvensis (skylark) [30,31], Microtus agrestis (field vole) [29], Bembidion lampros (beetle) [32], Erigone atra/Oedothorax fuscus (spider) [33], and Capreolus capreolus (roe deer) [34]. These range from species with highly detailed behavior but low numbers (roe deer) to spiders with simple behavior but the necessity to handle over 1 million agents concurrently.…”

The role of ecological models in linking ecological risk assessment to ecosystem services in agroecosystems

“…Population models describing various bird, insect and spider species have already been developed and used to explore how changes in population dynamics can influence biocontrol and how human activities alter the population dynamics of the modeled species (e.g. Sherratt and Jepson, 1993;Thorbek and Topping, 2005;Topping et al, 2005). If a contribution of one specific species outweighs all the others, we can focus on modeling the population dynamics of that species.…”

Population-level Assessment of Risks of Pesticides to Birds and Mammals in the UK

“…Priority is given to identifying approaches which can be applied immediately. Two of these approaches are illustrated in the case study described in this issue by Topping et al (2005).…”